THE PIGEON. 



187 



rib, having all the characters of the last cervical rib ( 14, 

 15), a ventral section, the sternal rib, a straight flat 

 bone, making an obtuse angle with the vertebral rib, and 

 articulating at its lower end with a facet on the sternum. 



trj 



FIG. 46. Columba livia. The sacrum of a nestling (about fourteen 

 days old), viewed from beneath ( x 2). 



On the left side (right of the figure) the first two caudal ribs (c.r) are 

 removed, so as to show the dorsal transverse processes (tr.p") : the sub- 

 sequently ossifying membrane which fills up the intervals between the 

 iransverse processes is also removed on the same side : the last thoracic 

 vertebra is not shown, not yet having united with the sacrum. 



The cartilaginous parts are dotted. 



c.i, ossified centrum of first, and c. 7, of seventh caudal vertebra : 

 c.r, first caudal rib: /.I, centrum of first, and /.3 of third lumbar 

 vertebra: s.i, centrum of first, and s. 3 of third sacral vertebra : trp, 

 transverse process of first lumbar, tr.p', of second sacral, and tr.p", 

 of first caudal vertebra. 



VI. In the remaining vertebrae entering into the com- 

 position of the compound sacrum make out : 

 26. The two or three lumbar vertebrae (Fig. 46, /. i - 

 /. 3), immediately succeeding the fifth thoracic : each has a 

 stout wide body, short strong transverse processes abutting 



